309
FXUS65 KBYZ 220720
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
120 AM MDT THU OCT 22 2026
KEY MESSAGES
- WARM AND MOSTLY DRY CONDITIONS TODAY.
- STORM SYSTEM LATE TONIGHT INTO SATURDAY MORNING BRINGS LOWER
ELEVATION RAIN AND MOUNTAIN SNOW; GREATEST TOTALS FORECAST WEST
OF BILLINGS, WITH LITTLE TO NO PRECIPITATION OVER SE MONTANA.
- ELEVATED FIRE WEATHER CONCERNS SOUTHEAST MONTANA FRIDAY
AFTERNOON-EVENING.
- WINDY CONDITIONS EXPECTED FRIDAY INTO SATURDAY.
- SEASONAL TEMPERATURES (HIGHS IN THE 50S) AND UNSETTLED
CONDITIONS (20-40% PRECIPITATION CHANCES) SUNDAY THROUGH
WEDNESDAY. UNCERTAINTY IS HIGH FOR THE EXTENDED FORECAST.
DISCUSSION
NEXT 7 DAYS...
TODAY WILL BE A FAIRLY QUIET DAY RELATIVE TO THE WEATHER SYSTEM
THAT WE SEE MOVE INTO THE REGION TONIGHT. THROUGH THE MORNING
HOURS TODAY WE WILL SEE ISOLATED TO SCATTERED SHOWERS OVER THE
HIGH TERRAIN OF SOUTH-CENTRAL MONTANA WHICH COULD ALSO COME WITH A
STRAY LIGHTNING STRIKE. THE AFTERNOON WILL BE MOSTLY DRY AND
CLEAR THOUGH. THERE ARE SEVERAL IMPACTS/PIECES OF THE PUZZLE WITH
THE FRIDAY AND SATURDAY SYSTEM SO WILL DISCUSS EACH IMPACT
INDEPENDENTLY.
THERE ARE SEVERAL THINGS TO DISCUSS JUST WHEN IT COMES TO THE WIND
POTENTIAL REGARDING THIS SYSTEM. STARTING WITH THE FRIDAY AM GAP
WIND POTENTIAL, LIVINGSTON WILL LIKELY HAVE A NARROW WINDOW OF A
GOOD SETUP. AS THE PARENT TROUGH ADVECTS INTO THE REGION, WE WILL
SEE SURFACE PRESSURE FALLS OVER THE PLAINS NEAR BILLINGS AND
SURFACE PRESSURE RISES OVER YNP AND THE NEARBY HIGH TERRAIN. WHILE
THERE WILL BE SOME PRESSURE GRADIENT ALL NIGHT, MODELS DO NOT
DEPICT THE GRADIENT REALLY TIGHTENING UP UNTIL JUST BEFORE
SUNRISE. THERE IS SOME DISCREPANCY THOUGH REGARDING JUST HOW
STRONG THIS WILL BE. WHEN LOOKING AT THE PROXY IDA-LWT DELTA-P,
THE MODELS ARE RANGING BETWEEN 6 AND 12 MB ON THE MOST RECENT
MODEL RUNS. THIS IS RESULTING IN LOW TO MEDIUM CONFIDENCE IN JUST
HOW STRONG THE WINDS WILL BE. ADDITIONALLY, AS THE CLOUD COVER
MOVES IN, IT MAY BECOME A LITTLE MORE DIFFICULT TO DEVELOP THE
STRONG NOCTURNAL INVERSION NECESSARY FOR TRULY STRONG WINDS.
AT ROUGHLY THE SAME TIMEFRAME (FRIDAY AROUND SUNRISE) WE WILL NEED
TO KEEP AN EYE ON THE BIGHORN MOUNTAINS AND SHERIDAN, WY. THERE
ARE HINTS AT POTENTIALLY SOME MOUNTAIN WAVE ACTIVITY, HOWEVER
THERE REMAIN SEVERAL QUESTIONS. THE FIRST IS THAT MODELS ARE
FAIRLY INCONSTANT WITH JUST HOW STRONG AND/OR HIGH THE INVERSION
WILL BE AT THE MOUNTAIN TOP. THIS IS LIKELY DUE TO DISAGREEMENTS
IN CLOUD COVER THROUGH THE NIGHTTIME HOURS. THIS MODEL
DISAGREEMENT EXTENDS TO THE LEE SIDE SUBSIDENCE AS WELL. THERE IS
AGREEMENT THAT THERE WILL BE SOME SUBSIDENCE IN A FAVORABLE
SETUP, BUT THE STRENGTH OF WHICH VARIES GREATLY BETWEEN MODELS AND
RUNS. THE LAST PIECE OF THE PUZZLE IS THE MID LEVEL WINDS
THEMSELVES. THERE IS GOOD CONFIDENCE IN A 700MB JET STREAK THAT
MOVES OVER THE BIGHORNS RIGHT AROUND SUNRISE FRIDAY. THERE IS
DECENT AGREEMENT THAT THE MAXIMUM WIND SPEEDS AT THE 700MB LAYER
WILL BE JUST SOUTH OF OUR CWA INTO JOHNSON CO. IT LOOKS
INCREASINGLY LIKELY THAT THE AREA NEAR STORY, WY WILL BE THE MAIN
FOCUS FOR OUR FORECAST AREA. 700MB WIND MAXIMUM IS CONSISTENTLY
BEING DEPICTED BETWEEN 40 TO 50KTS. WHILE THIS COULD BE CONDUCIVE
TO A WINDY MORNING, THESE SPEEDS DO NOT POSE A DAMAGING WIND
THREAT. THIS WILL, OF COURSE, BE MONITORED AS WE GET CLOSER TO
THE EVENT.
THE LAST WINDY THING TO TALK ABOUT IS MUCH SIMPLER, THE MIX-DOWN
WINDS OVER THE PLAINS. AS THE PREVIOUSLY DISCUSSED 700MB JET MAX
MOVES EASTWARDS INTO NE WY AND SE MT THROUGH THE DAY FRIDAY, THIS
WILL BRING WINDY CONDITIONS TO SE MT AND NE WY MIDDAY FRIDAY.
EVEN THOUGH MODEL SOUNDINGS ARE SHOWING VERY DEEP MIXING FRIDAY,
AS PREVIOUSLY DISCUSSED, THESE WINDS ALOFT WILL NOT BE
PARTICULARLY STRONG. THE REST OF THE REGION WILL SEE BREEZY WINDS
AS WELL DURING THE EVENT AS WINDS ALOFT WILL BE IN THE 30 TO 40KT
RANGE WITH BROAD-SCALE SUBSIDENCE BEHIND THE MAIN VORT MAX. WHILE
THIS WILL MAKE FOR A WINDY DAY FRIDAY, AGAIN, DO NOT FORESEE ANY
HIGHLIGHT WORTHY GUSTS AT THIS TIME.
ALTHOUGH MOST OF THE TALK AROUND THIS SYSTEM HAS BEEN CENTERED
AROUND THE PRECIPITATION AND WIND, THERE IS ALSO A DRY ASPECT
THAT REQUIRES ATTENTION DUE TO THE POTENTIAL FIRE WEATHER
CONCERNS. THE MAIN AREA OF CONCERN IS NORTHERN WYOMING AND FAR
SOUTHEAST MONTANA. THIS IS, AS PREVIOUSLY DISCUSSED, THE AREA THAT
WILL SEE THE STRONGEST WINDS DURING THE EVENT. FRIDAY DAYTIME RH
VALUES ARE FORECAST TO BE THE LOW 20S PERCENT. ALTHOUGH ISOLATED
VALUES BELOW 20 PERCENT ARE EXPECTED, THIS WILL NOT BE
WIDESPREAD. THE GREATER CONCERN IS JUST TO OUR SE IN NORTHEAST WY.
ALL THIS TO SAY, ELEVATED FIRE WEATHER CONDITIONS ARE FORECAST
FRIDAY AFTERNOON IN THESE AREAS.
THE LAST PIECE OF THIS PUZZLE TO TALK ABOUT IS THE PRECIPITATION.
THIS TIME LAST NIGHT THE QPF TOTALS CAME UP QUITE SIGNIFICANTLY,
AND TONIGHT IT IS THE OPPOSITE. AMOUNTS HAVE COME WAY DOWN ACROSS
THE ENTIRE FORECAST AREA. IT SEEMS LIKE EVERYONE WILL SEE A FEW
DROPS OF RAIN BUT MOST TO ALL OF THE ACCUMULATION WIL FALL TO THE
WEST OF BILLINGS. EVEN THE SNOW TOTALS IN THE MOUNTAINS CAME DOWN
A LOT. THE HIGHEST FORECAST SNOW TOTALS AT THE PEAKS OF THE
BEARTOOTHS RIGHT NOW ARE 6" AT MOST. THE GREATEST IMPACTS FROM THE
SNOW WILL BE TO ANYONE RECREATING IN THE HIGH COUNTRY, AND THOSE
TRAVELING THE BOZEMAN PASS FRIDAY NIGHT. IMPACTS TO TRAVEL AND
RECREATION DO NOT TAKE MUCH SNOWFALL, ESPECIALLY WITH BREEZY
CONDITIONS.
LOOKING AHEAD, TEMPERATURES WILL BE CLOSER TO AVERAGE, IF NOT
JUST BELOW, GOING INTO NEXT WEEK. THERE IS ALSO A GOOD SIGNAL THAT
THE UPPER LEVEL PATTERN WILL REMAIN VERY ACTIVE. ANY SORT OF
DETAIL AFTER MONDAY IS A HUGE QUESTION THOUGH AS ALL MODELS ARE
SHOWING WILDLY DIFFERENT THINGS WITH SOME PRETTY LARGE FEATURES.
THERE WILL BE MORE CHANCES FOR PRECIPITATION THROUGH THE REST OF
THE WEEK BUT DETAILS REMAIN UNCLEAR. WMR
AVIATION
VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD WITH PASSING MID
AND HIGH CLOUDS. THERE IS A LOW CHANCE (10-30% CHANCE) FOR A FEW
SHOWERS ACROSS THE WESTERN MOUNTAINS AND FOOTHILLS INCLUDING VC
KLVM, THIS MORNING. MINIMAL IMPACTS ARE EXPECTED WITH ANY
PRECIPITATION. THERE IS A LOW CHANCE FOR FOG TO DEVELOP NEAR KBHK
AND KMLS THIS MORNING AS WELL (15% OR LESS). MATOS/STP
PRELIMINARY POINT TEMP/POPS
TDY FRI SAT SUN MON TUE WED
-------------------------------------------------------
BIL 074 048/068 034/049 030/050 030/048 030/055 034/052
0/U 07/W 80/U 00/U 21/B 11/B 22/W
LVM 073 043/058 025/045 024/048 024/052 026/054 028/051
2/W 29/W 90/U 00/U 11/B 12/W 32/W
HDN 075 045/073 031/051 026/053 027/051 027/056 029/054
0/U 06/W 90/U 00/U 11/B 11/B 22/W
MLS 075 048/075 035/047 028/050 030/047 029/053 031/050
0/U 01/B 40/U 01/U 11/B 11/B 21/B
4BQ 077 053/080 036/046 031/049 031/047 031/055 033/053
0/U 01/N 30/U 04/W 32/W 11/B 21/U
BHK 079 047/082 030/046 023/048 024/044 024/051 027/051
0/U 12/N 20/N 02/W 32/W 11/B 21/B
SHR 075 045/074 029/048 025/051 027/052 026/057 029/055
0/U 02/W 50/B 03/W 21/B 11/B 22/W
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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